1. Field Of The Invention
The invention relates to a process for the preparation of chroman derivatives of the general formula: ##STR2## in the formula, in which: R.sup.1 is hydrogen or C.sub.1-4 -alkyl,
R.sup.2 is C.sub.1-6 -alkyl, C.sub.3-6 -cycloalkyl, optionally substituted aryl or optionally substituted aryl-C.sub.1-6 -alkyl, PA1 R.sup.3, R.sup.5 and R.sup.6 independently of one another are hydrogen, halogen, C.sub.1-4 -alkyl or optionally substituted aryl, and PA1 R.sup.4 is C.sub.1-6 -alkyl, C.sub.3-6 -cycloalkyl, (C-.sub.1-6 -alkoxy)methyl, optionally substituted aryl, optionally substituted aryl-C.sub.1-6 -alkyl, C.sub.1-6 -alkanoyl or optionally substituted aroyl.
Compounds of this type are intermediates for the synthesis of pharmaceutical active ingredients, e.g., of hypolipidemics [T. Yoshioka et al., J. Med. Chem., (1989), 32, 421-428].
2. Background Art
Known syntheses of the chroman derivatives (I) start from correspondingly substituted hydroquinones, for example, 3-(2,5-dihydroxyphenyl)propan-1-ols [see, e.g.: Comprehensive Heterocyclic Chemistry, (Ed.: A. J. Boulton and A. McKillop), Pergamon Press, Oxford, Vol. 3, Part 2B, pp. 778 et seq.]. These starting materials are cyclodehydrated to give chroman-2-carboxylic esters, whose ester function is reduced and whose resulting hydroxymethyl group is etherified to give the title chroman derivative compound (I). The process is, however, relatively involved.